This is a blog detailing the creation/evolution/ID controversy and assorted palaeontological news. I will post news here with running commentary.

Saturday, November 16, 2013

Acts and Fiction: The ICR Does A Hatchet Job on Dmanisi Skull 5

The ICR has, bluntly, called the description of the new Dmanisi skull 5 a fraud. Lets find out why. The conclusion, based on the descriptors of the morphology of skull 5 is that it has a mix of early Homo and Homo erectus traits. Brian Thomas of the ICR thinks it is nothing more than an ape. In support of this, he puts together seven points, which I will take one at a time. The analysis is somewhat repetitive at times because Mr. Thomas' points, themselves, are.

Point No. 1

It is anatomically quite different from known human skulls. The Science authors wrote, "The morphology of skull 5 stands apart from that of any other known fossil Homo specimen through its combination of a small braincase with a large prognathic face." Maybe it "stands apart from" man because it was not a man. Could it actually be an ape's skull?

Well, no. It has no ape characteristics at all. They are clearly hominin in nature. For example:

The foramen magnum (the hole for the spinal column) is at the base of the skull, rather than the back, as is the case for apes. It is how we know that it was bipedal. There is not a single ape, fossil or otherwise that has this characteristic.

On observation of the skull, there is clearly an angular torus (a ridge of bone extending from the ear to the back of the head), a trait not found in early African Homo but found in the rest of the Dmanisi skulls and all East Asian Homo erectus specimens, suggesting that this population represented a point at which there was radiation out of Africa in two directions, toward Europe and Asia. This is not a trait found in any ape.

When scaled for brain weight/body size, the brain case is too large to be an ape. It is clearly a hominin. Further, other skulls in the Dmanisi sample range from 601 to 730 cubic centimeters in size, a quarter more to double the size of any extant or fossil ape.

The teeth are clearly hominin in morphology (see images below). While there is considerable procombency of the incisors (they angle forward from the face), there is no expansion of the canines beyond the tooth row, the premolars are not rotated to sharpen the canines and there is no diastema (space) between the canines and incisors to make room for an expanded canine in the opposite tooth row. This is clearly a hominin mouth, not an ape one.

So? Say it isn't linked with any of the post cranial material. That doesn't change the morphology of the skull in any way.

Point No. 3

It has a very ape-like brain volume—far smaller than that of a human. It was estimated at 546cc, similar to that of gorillas and Australopiths, but only about half the average size of a human

As Mr. Thomas so correctly notes, the cranial size is not necessarily an indication of intelligence or of hominin status. He also doesn't define what he means by "human." Conventional anthropologists define "human" as being bipedal (and not the weird Oreopithecus-style gait). No other primate does this and it dates to around 4.4 million years ago. Further, given that size is not a reliable indicator, point 3 above still stands.

Point No. 4

It has a heavily built, ape-like jaw. Skull 5 "has the largest face, the most massively built jaw and teeth and the smallest brain within the Dmanisi group," according to a news release from the University of Zurich where three of the Science authors work.4 But where is the evidence proving that all five Dmanisi skulls even belong to the human group?

There is variability in all fossil samples. For example, the Mladeč sample from central Europe that dates to between 34 and 37 thousand years ago is quite variable, with some crania resembling Neandertals and others resembling modern humans. Further, as Lordkipanidze et al. point out, the range of variation present in the Dmanisi sample is not greater than what one would find in a sample of chimpanzees or the world-wide sample of modern humans (although intra-populational differences in the modern human sample, I am quite sure, are less).

Point No. 5

It links to other material that is not clearly identified or dated. The Science authors reported, "Furthermore, the remarkably large and robust dentognathic remains of early H. erectus from Java (Trinil/ Sangiran) exhibit close affinities with skull 5." But the abstract describing the Java remains reads, "Temporal changes, within-group variation, and phylogenetic positions of the Early Pleistocene Javanese hominids remain unclear."
Additionally, experts in human evolution have a long history of assigning human and ape remains to the Homo erectus human category. By tying skull 5 to past category confusion, the Science authors muddied their own identification of skull 5 as human.

The fact that some temporal changes in Homo erectus remain unclear does not diminish the importance or morphology of the East Asian Homo erectus fossils, themselves, many of which are nicely dated to between 1.5 and 1.8 million years ago. From the paper that Thomas cites:

Further, it is absolutely clear that there are differences between these hominins and later populations: The Bapang-AG H. erectus population is advanced, showing a similar degree of dentognathic reduction as the Middle Pleistocene Chinese H. erectus represented by the Zhoukoudian and Lantian remains. In this respect, this population is significantly derived relative to African early H. erectus and the oldest hominids of Java (Grenzbank/Sangiran group). However, it remains unclear whether these apparent similarities reflect affinities or homoplasy between the Bapang-AG and Chinese H. erectus.

Thomas' second point on tying this skull to category confusion is a terminological inexactitude. Experts in human evolution do no such thing. In fact, there has been a raging dispute about how expansive the Homo erectus taxon actually is, with splitters, like Ian Tattersall on one side arguing that the human fossil record between 2 million and 500,000 years B.P. is taxonomically more diverse than we think and Milford Wolpoff, who argues that we need to lump everything into Homo and dispense completely with the taxon Homo erectus. The only person I know of who is assigning too many fossils to Homo erectus is Marvin Lubenow who, in his execrable book Bones of Contention was unable, as nearly as I could tell, to distinguish Homo erectus from anything else and who made numerous errors because of this. Further, Lordkipanidze and colleagues did not tie the skull to category confusion, they attempted to place it taxonomically within the entire range of Homo.

But even if it were case that they were tying skull 5 to Homo erectus, that is still nothing like saying it is an ape, since no Homo erectus fossils are ape-like in any way, shape or form. Case in point:

The top image is an African Homo erectus specimen (KNM-ER 3883) while the bottom one is a chimpanzee. The differences are striking.

Point No. 6

The researchers' approach to skull 5 may be similar to other fraudulent or dubious finds. Dutch physician Eugene Dubois, anxious to find proof of human evolution, uncovered the famous Java "man" fossils in 1891. It was not until 30 years later that Dubois revealed the truth behind the find and admitted he had been hiding fully human skulls from the same Javan site. Some later suggested that his Java man skull cap was actually that of a gibbon. Could today's scientists be subject to the same eagerness to prove evolution, leading to skewed analyses? Because human origins research can be so subjective, one researcher of the history of paleoanthropology voiced a relevant caution: "We have only to recall the Piltdown adventure to see how easily susceptible researchers can be manipulated into believing that they have actually found just what they had been looking for."

The Science authors also wrote that skull 5 looks like the famous KNM-ER 1470 found in Africa. But skull 1470 was pieced together from so many separated fragments that it may not constitute a real, single individual. Understandably, its identification has long been difficult. Who knows which pieces were from humans and which were from apes?

Even so, the part of skull 1470 showing a forehead and human-like brow ridges differs from the apish appearance of skull 5. Did the Science authors link skull 5 to Africa's KNM-ER 1470 for evolutionary rather than anatomical reasons?

Okay, this one made me really mad because it accuses the researchers of not being competent or careful about what they have described. The remains that DuBois uncovered were manifestly Homoerectus. They weren't fully human and they sure as heck weren't a gibbon. The research community refused to accept DuBois' claims because they thought he was working in the wrong part of the world, and they were susceptible to eurocentrism, a problem which dogged the discipline for decades.

Human origins research isn't any more or less subjective than any other scientific enterprise. It grows and changes in relation to new data that is unearthed. You might say the same thing about cosmology or cell theory or microbiology, fields that are always attempting to understand how things work. Researchers are human and they make mistakes. But they also try to fix them. What is conveniently left out of Thomas' paragraph is that the Piltdown hoax was uncovered by scientists, working with scientific methods. Science, as a self-correcting enterprise, works very well, and palaeoanthropology is no different.

Regarding ER 1470, his reference is another young-earth creationist, Duane Gish, who has been shown repeatedly to have a severely limited knowledge of the fossil record (See Don Prothero's book Evolution: What the Fossils Say and Why it Matters for examples) The idea that it represented pieces of humans and apes is unsupported. The skull has many, many contiguous pieces—enough to reliably construct the cranium and the face. Further, the pieces that were found are manifestly not from fossilized apes, none of which have ever been found in East Africa. The primary dispute was not what it looked like, the primary dispute was how old it was. Richard Leakey said that it was 2.9 my old and everyone else said "Well, no, Richard, that can't be right." Eventually, when stratigraphic and radiometric analysis was done, it was discovered to be around 1.9 million years old.

Point No. 7:

It is replete with ape features. Skull 5 has a U-shape dental arch, not the more parabolic shape humans present. Its chin slopes back like an ape without the forward-jutting bottom point of a human chin. There is no human nose bridge, and it has prominent attachment points for enormous jaw and neck muscles.

It most certainly does have a human-shaped dental arch. Turn any human skull on its head and you will find dental anatomy exactly like what you find in Skull 5. Lets take a look. On the left is a modern human from an inferior view. On the right is Dmanisi Skull 5. The tooth rows are very similar in shape, with similarly-proportioned teeth.

Now lets compare both of these skulls to that of a chimpanzee to see exactly what the differences are.

Well, for one, you can clearly see the diastema between the canine and the incisors. You can also see that the maxillary tooth rows in the chimpanzee are parallel, instead of a gentle U that you see in the other two skulls. The canine on the chimpanzee is very expansive, sharp and extends beyond the tooth row. Further, you can see that, in Skull 5, the foramen magnum is underneath the skull, not toward the back as in the chimpanzee. Skull 5 looks nothing like the chimpanzee skull and, in fact, shares most (if not all) of its similarities with the modern human from this anatomical position.

The lack of a chin is absolutely expected at this point in human evolutionary history and is related entirely to tooth size. As the front teeth have shrunk in size, the bone has resorbed in the front of the jaw, creating the chin. In fact, tooth size has continued to shrink even since the advent of modern humans, with an 11% drop since the Neolithic. What Mr. Thomas does not seem to realize is that the chin has only appeared in the last 100 thousand years and is absent not just on early Homo but Homo erectus and archaic Homo sapiens. The lack of a chin, in no way impairs its status as a hominin, unless you don't consider Neandertals hominins. There is no human nose bridge on the skull because that didn't appear until archaic Homo sapiens, some 400 thousand years ago.

Thomas ends his article with this:

Biblical creationists are not restricted to interpreting skull 5 according to evolution. Instead, they are free to exercise a healthy scientific skepticism of current interpretations. If Dmanisi skull 5 ends up not being human at all, then its titillating implications for human evolution fizzle. It would then simply become an extinct ape kind's skull found in a long-collapsed animal den into which saber-toothed cats may have dragged both human and other prey.

This is only true if the information is being treated honestly. Unfortunately, because Mr. Thomas does not possess the necessary education in either comparative primate or fossil human anatomy, he cannot do this. That he has seemingly failed to educate himself on even the basic anatomy necessary to understand these errors further compounds the problem. His analysis is riddled with inaccuracies and unwarranted conclusions and, as such, constitutes no evidence against evolution or that the Dmanisi fossils are anything other than what the investigators say they are.

2 comments:

Thanks for the comparative images - not so easy to find by Googling. As for the DuckSpeak from Brian Thomas... he is a Young Earth Creationist, so he's already adept at distorting the evidence in favour of a preconceived outcome.

Another point, which totally eludes the YECs, is that if evolution is true, then some fossils morphological between groups will be HARD to classify either way... just like this one. Of course, we don't have any Miocene apes in good-enough condition to check the ancestral condition of either chimpanzees or humans for most of the diagnostic criteria discussed here, so comparing humans and chimps only gives a rough guide as to evolution in either direction. Ancestral apes, for example, probably didn't have the exaggerated canines we see on modern chimps.